| (1) | \begin{equation} \forall \, x \in X : \forall \, y, y' \in Y \left( (x, y), (x, y') \in f \quad \implies \quad y = y' \right) \end{equation} | (D358: Right-unique binary relation) |
| (2) | \begin{equation} \forall \, x \in X : \exists \, y \in Y : (x, y) \in f \end{equation} | (D359: Left-total binary relation) |
| (3) | \begin{equation} \forall \, x, x' \in X : \forall \, y \in Y \left( (x, y), (x', y) \in f \quad \implies \quad x = x' \right) \end{equation} | (D357: Left-unique binary relation) |